This application claims priority to the Federal Republic of Germany Patent application serial number 101 18 982.6 filed on Apr. 18, 2001.
The invention relates to a window lifter system as well as to a method of controlling a plurality of window lifter motors.
In many motor vehicles equipped with electrical window lifters, there is realized a comfort function by means of which all window panes can be closed simultaneously. Due to the fact that on moving the window panes there may prevail differing conditions at the various vehicle doors of one and the same vehicle, for instance differing conditions in terms of friction, differing lengths of travel and differing weights of the window pane, too, there may occur the phenomenon that the closing action of the individual panes, in the event that they are to be closed simultaneously, is terminated at different points in time. Such phenomenon may also be caused by the circumstance that the vehicle manufacturer combines different variants of the window lifter motor from various suppliers. The different variants of the window lifter motor are not identical with respect to their characteristics and, hence, result in differing speeds of travel of the window pane. Closing actions that deviate from each other despite an identical starting position are felt by the end user to be a nuisance.
Therefore it is the object of the invention to provide a window lifter system as well as a method of controlling a plurality of window lifter motors, by means of which a simultaneous closing action of the window panes is assured, independently of the marginal conditions being present at the individual window panes.
To this end, there is provided according to the invention a window lifter system comprising a first window lifter motor and a master control device for the first window lifter motor, the master control device being able to detect a position of a window pane driven by the first window lifter motor and to drive the first window lifter motor at a variable speed, at least one second window lifter motor and a slave control device for the second window lifter motor, the slave control device being able to detect a position of a window pane driven by the second window lifter motor and to drive the second window lifter motor at a variable speed, and a bus system by means of which the master and slave control devices are able to communicate with each other. In this system, the master control device presets the speed at which the window pane associated to it is being closed. This speed information is given to each slave control device which for its part takes care that the window pane associated to it is closed at the same speed.
The method according to the invention for simultaneously closing all the window panes is distinguished by the following steps: First, the master control device moves the window pane driven by it at a speed which lies below an achievable maximum speed, from a fully open position into a fully closed position. In so doing, there is measured the time which is needed for fully closing the window pane. The measured time is transferred to the slave control device as a set time and is stored there. The slave control device compares the set time with the actual time needed for the last closing action of the window pane driven by it, and appropriately corrects the drive speed. The corrected drive speed is stored and is used for the next closing action of the window pane. In this method, the speed of travel of the window panes associated to the slave control devices is updated whenever the window pane associated to the master control device is brought from the fully open position into the fully closed position.
According to a preferred embodiment of the invention it is provided for that the control devices have a semiconductor bridge circuit in order to feed current into an associated window lifter motor in a pulse-width modulated fashion. This makes it possible for the control device to drive the window lifter motor at a variable speed. Preferably, the master control device drives the window lifter motor with an ON/OFF ratio of approximately 80%. This is a good trade-off between the high speed of travel which is striven for, on the one hand, and the must of leaving sufficient scope for a higher ON/OFF ratio, on the other. This higher ON/OFF ratio is needed to achieve the same speed of travel as with the window pane of the master control device, if the resistance to travelling of the window pane associated to one of the slave control devices is higher than the resistance to travelling of the window pane associated to the master control device.
For the bus system, a CAN bus system may be used or a bus system that is based on Bluetooth technology.
According to a preferred embodiment of the invention, it is provided for that the window lifter motor has a Hall effect sensor by means of which the associated control device is able to detect the absolute position of the driven window pane. This makes it possible for the control device to monitor the speed of travel of the window pane driven by the associated window lifter and to adapt the ON/OFF ratio for the window lifter motor such that there is achieved a constant speed of travel. It is in this way that despite an enhanced friction in a certain range of travel of the window pane, for example, there can be achieved a constant speed of travel by increasing the ON/OFF ratio of the window lifter motor whenever the window pane is in the region with enhanced friction.
According to an alternative, simpler embodiment there may be provided for that the control device is able to detect the acquisition of a fully open position and a fully closed position of the associated window pane with the aid of the current consumption of the respective window lifter motor. Also with this embodiment, it is ensured that the time which is needed to bring each window pane from the fully open position into the fully closed position, is always the same. There can not be guaranteed, however, that the window panes always move at the same speed between the fully open and fully closed position.
It is preferably provided for that the control device is directly mounted to the associated window lifter motor. This results in a compact assembly unit. As an alternative, it may be provided to arrange the control device so as to be remote from the associated window lifter motor. This suggests itself in particular if the control device is a slave control device and controls more than one window lifter motor.
Preferably, it is provided for that the master control device is associated to the window pane of the driver""s door of the vehicle. This window is usually actuated most frequently, so that concerning the window pane of the driver""s door there exists the greatest probability to gain a current value for the speed of travel from the fully open into the fully closed position. As with each actuation of the window pane of the driver""s door this current value is transferred to the slave control devices of the other window panes, the slave control devices have a current value even if they have not been actuated over a longer period of time.
If the slave control device does not have an actual time from the last closing action of the window pane driven by it, it drives the window lifter motor associated to it preferably likewise at an ON/OFF ratio of approximately 80% in a pulse-width modulated fashion. This guarantees, on the one hand, that all windows are moved approximately at the same speed on the first actuation thereof. On the other hand, a sort of xe2x80x9cemergency running propertiesxe2x80x9d is provided, at the presence of which all windows will be closed with approximately the same speed if no current set value is preset by the master control device.
Advantageous designs of the invention will be apparent from the sub-claims.